Prior art napkin making machines using mechanical tuckers and grippers are based on U.S. Pat. Nos. 2,054,426 and 2,057,879 granted to Campbell (1936).
In 1934, U.S. Pat. No. 1,974,149 to Christman describes vacuum folding techniques used in machines for making longitudinally and single transversely folded products like napkinsxe2x80x94referred to as quarterfolded napkins.
In the 1970""s U.S. Pat. Nos. 3,689,061 to Nystrand and 3, 870,292 to Bradley extended vacuum folding to machines that make a second transverse fold for dinner napkinsxe2x80x94referred to as eigthfold napkins.
For example, the ""051 apparatus of Nystrand uses a vacuumized anvil/folding roll (F) to selectively advance, foldback, and superpose the leading half panel of a segment over the trailing half and release the lead panel while the trailing half panel is held and advanced.
In ""061, the carrier/folding vacuum roll (F) coacts with a vacuumized transport roll (C) to complete the second transverse fold (doublefold).
Present state fo the art vacuum folders operate with the same folding principles used for the past 60 years and include vacuum carrier rolls, combination anvil carrier rolls, and vacuum folding rolls made from solid blanks or solid steel forgings. machine to be processed without off-line unwinding and slitting to widths suitable for converting and are describes in a co-pending U.S. patent application Ser. No. 09/499242.
The objects of the instant roll design are detailed below.
The object of this invention is to provide hollow rolls with separate internal vacuum and air conduits that can be assembled from discreet components to overcome weight, diameter, and roll length limits of present vacuum transport, cutting, and folding rolls.
A further object is to provide conduits superposed against the inside surface of hollow rolls to minimize the length of drilled connections between air/vacumn conduits and openings in the surface of the rolls.
An object of the invention is to provide larger conduits for low pressure high volume air conduits rather than large diameter holes drilled into solid roll blanks.
An object is to provide larger diameter cylinders with multiple repeats and substantial internal space to avoid the diameter limits for holes drilled in solid rolls because of the restricted area of small diameter rolls for shorter product repeats.
A further object is to provide closed air plenum chambers using the inside surface of the roll as a portion of the plenum chamber closure.
An object is to provide a plenum against the inside surface to minimize the length of, or eliminate, air channels to openings in the surface of the roll.
An object of the above stated plenum with a replaceable surface section is to allow different patterns of air apertures to extend as longitudinal slots, substantially xe2x80x98open meshxe2x80x99 segment support surfaces, or patterns of holes in the roll surface.
A further object of the air plenum is to allow the operative surface pattern of the plenum chamber to be changeable for different air flow volumes.
An object of the invention is to provide lighter weight hollow rolls of larger diameter having an extended circumferential path for use of more than one stationary fold completion device thereby eliminating the separate cooperating vacuum roll usually needed for a second transverse fold.
Another object is to provide for surface mounting of anvils and internal support means to increase roll stiffness.
Another object is to provide hollow roll construction having a hollow central shaft and roll supports between the roll shell and central shaft.
A further object of this is to provide air/vacuum conduits that can be prefabricated or pre-molded from plastics to complete the internal passages between air/vacuum sources and connections to vacuum ports and air apertures.
The above listed objects describe benefits that derive from the hollow roll and the benefits of greater productivity from wider, larger diameter rolls and air folding, etc. more clearly described in the abovementioned co-pending U.S. Patent Application.
Other objects may be seen in the ensuing specifications.